The most widely used methods (dental age, body weight) for age estimation in nonhuman primates are inadequate. More precise standards and age indicators can be obtained by measuring skeletal age, which has proven to be the best criteria in the assessment of unknown chronological age. Our longitudinal radiographic stuies have been undertaken to provide information on the development and bone maturation of the hand and wrist in Macaca mulatta monkeys. Our data will cover the whole period of appendicular bone maturation from 120 days of gestation (the onset of carpal center ossification) to adulthood (over 5 years). To obtain the fetal data, a novel surgical technique of multiple uterotomies was developed. Serial radiographic data is obtained by three uterotomies and after normal delivery. Our radiographic study will provide pre- and post natal age indicators and will be prepared for publication as an atlas, which should make the data readily usable in many studies where the precise age of the experimental animal is required.